The present invention relates to an organic light emitting device that emits light by using organic Electro Luminescence (EL) phenomenon, a display unit including an organic light emitting device, and an illuminating device including an organic light emitting device.
Organic light emitting devices (organic EL device, organic electroluminescence device) have attracted attention since each device has a light emitting layer composed of an organic compound between an anode and a cathode and is able to realize a large-area display unit driven with low voltage.
The organic light emitting device structuring the display unit, described above, is provided on a transparent substrate made of, for example, glass or the like. In the organic light emitting device, an anode composed of ITO (Indium Tin Oxide: transparent electrode), an organic layer, and a cathode are layered sequentially from the substrate side. The organic layer has a structure in which an electron hole injection layer, an electron hole transport layer, and an electron transport light emitting layer are sequentially layered from the anode side. In such an organic light emitting device, electron injected from the cathode is recombined with electron hole injected from the anode in the light emitting layer, and light generated in such electron-hole recombination is extracted from the substrate side through the anode.
In general, life of the organic light emitting device is determined by injected electric charge, which is able to be resolved by decreasing the initial luminance in driving. However, decreasing the initial luminance limits practical application, and denies potential possibilities of the organic light emitting device, resulting in inability of realizing a next generation television.
Thus, for the purpose of realizing both high luminance and long life, so-called stack type organic light emitting devices have been proposed. For example, Japanese Unexamined Patent Application Publication No. 2006-173550 discloses a technology in which a plurality of organic layers including a light emitting layer are regarded as one light emitting unit, and two light emitting units are layered to sandwich a connection layer for generating an electric charge between an anode and a cathode.
However, in the case where the respective light emitting units include different color light emitting layers, light emitting characteristics such as color luminance and current efficiency are not sufficient yet for all colors, and there is room for improvement.